Reviewer grace: 4h before the cron reviews unasked, or shorter? nf-1a12 ← Beads

Twinned from https://github.com/cfsh/ninefold/issues/718 by tools/beads/import_github.py's reconcile pass.

#713 changes the reviewer cron from "review every change" to "wait for the dev to run review_now.py, then review anyway once a grace window expires". That window is the whole safety dial, and its length is a call for you rather than for a bot. #713 asks it at the bottom of a long body, so it is repeated here where it can be answered from the list.

• A — 4h (recommended; ships by default). Clears the longest observed reply burst, and bounds an abandoned PR to about half a working session.
• B — 60-90m. A dead or paused session gets its PR picked up much sooner; some mid-batch re-reviews come back.
• C — 0. Restores the current review-every-change cadence exactly (--grace-min 0, or REVIEWER_GRACE_MIN=0 in the environment), keeping only the merge-gate freshness check #713 adds.

⚠ On a box carrying no reviewer credential a session cannot run review_now.py at all, so the grace there is pure delay with no way to shorten it. That interacts with your still-unanswered question on #576: "do you want the App private key on dev boxes?"

Default ships if unanswered — nothing is blocked on this.